[ ♪ Intro ]
Last week a bunch of astronomers met in Liverpool for the European Week of Astronomy and Space Science.
Quite a few gave some pretty cool presentations too -- like one about how the Milky Way might
be growing, which we talked about last week.
But there’s still a lot of cool things to talk about!
It turns out that solar tornadoes are not actually tornadoes, at least according to
one international team.
A solar tornado is a super cool name for a hot plasma structure sticking off the Sun’s surface.
They can be up to around two million degrees Celsius, and they appear to have similar-looking
shapes to the twisters we see on Earth.
Except, like most things on the Sun, each one is way bigger than our whole planet.
And they’re created because of the Sun’s really complex magnetic field rather than
wind and different-temperature air mixing together.
They also appear to be anchored below the Sun’s surface, so they don’t move around much.
Solar tornadoes were first observed about a century ago, but thanks to Sun-studying
spacecraft like NASA’s Solar Dynamics Observatory, astronomers are now able to study them in
more detail.
Based on 2D images, it looks like some of the Sun’s plasma is rotating up and away
from the surface to form 3D tornado shapes.
But now, evidence suggests those plasma “funnels” aren’t actually tornado-shaped at all.
They only look like they are.
In their presentation, the researchers described how they created new 3D ‘images’ of some
select solar tornadoes that occurred between 2014 and 2016.
They did this by adding in newer measurements, which allowed them to calculate not only the
plasma’s velocity, but its temperature and density, too.
So they got a better idea of what the magnetic field was up to and the structures it was forming.
It turns out that the Sun’s magnetic field lines aren’t twisting the plasma up into
tall tornado shapes at all.
Instead, the plasma’s moving mostly horizontally with respect to the Sun’s surface.
A solar tornado only looks like a funnel because of perspective.
And now that we have some 3-dimensional data, things are starting to look different.
The team did find some helical motion by tracking certain knots of plasma, but it was nowhere
near as fast as the measured horizontal velocity, which was up to 65 kilometers per second!
So it might be time to rename solar tornadoes.
We’ll just have to wait for peer-review to be sure.
Meanwhile outside Liverpool, last week’s Nature Astronomy reported astronomers have
captured radio images of a galaxy’s core using a telescope bigger than the Earth.
Most, if not all, large galaxies have supermassive black holes in their centers.
They’re millions, if not billions, of times more massive than our Sun.
A select few of those black holes are what astronomers call active.
They’re gobbling up so much matter that the galactic nucleus radiates a bunch of light.
The magnetic fields of these objects can also direct some of the infalling matter out into
jets, which travel at half the speed of light or more.
These jets can be so big they expand beyond the entire galaxy!
But exactly how these jets come to be has been a mystery, because astronomers haven’t
been able to get really high-resolution data from close enough to their sources.
While there are computer models, we don’t have the observational data to confirm if
they’re accurate.
To try and track some down, an international team of astronomers trained their sights on
the galaxy NGC 1275, located about 230 million light-years away.
The jets coming from its black hole -- known as 3C84 -- are actually super new on an astronomical scale.
They’re only ten years old.
But to get the ultra-clear resolution needed to study them, these astronomers needed a
telescope bigger than the entire planet.
Which, if you haven’t noticed, is not something they sell on Amazon.
Still, it’s totally possible thanks to a method called interferometry, or using an
array of telescopes to observe the same object at the same time.
If you do that, the resolution becomes equal to the average separation between the telescopes,
rather than just the size of a single dish.
We’ve actually been doing this on a smaller scale for decades, like at the Very Large
Array in New Mexico, and ALMA in Chile.
To study 3C84, the team used the RadioAstron interferometer, which is made up of telescopes
positioned all over the world, plus one in orbit.
All together, they have an angular resolution equal to 350,000 kilometers, which is nearly
the distance from the Earth to the Moon!
So, technically, it’s bigger than Earth.
With this network, they were able to resolve 3C84’s jet structure ten times closer to
the black hole than previous observations.
Admittedly, that distance is still 12 light-days away from the source, but hey.
Baby steps.
So far, we’ve learned that the jets at that distance were a lot wider than expected.
They are wider than any previously measured, in fact.
They’re so wide that it could mean that they start in a region around the black hole
called its accretion disk -- which shouldn’t happen based on our current models.
Instead, these models assume jets start at a place called the black hole’s ergosphere.
It’s an area right outside a rotating black hole’s event horizon, where space is literally
dragged around.
The new data doesn’t rule that hypothesis out, but it does sit at the edge of what’s
allowed, so it’s worth more investigation.
Of course, there’s also a chance that, because the jet is so young, we might not even be
seeing its final structure.
So, further study could also help astronomers better understand how these active galactic nuclei evolve.
Thanks to technology like interferometers, we’re getting better and better at studying
the distant reaches of our galaxy.
And there’s no telling what’ll come next.
Thanks for watching this episode of SciShow Space news!
There’s a lot we don’t know about the universe -- or even our solar system -- so
if you’d like to keep learning about it with us, go to youtube.com/scishowspace and subscribe.
[ ♪ Outro ]